Method of and apparatus for curing rubber articles by the circulation of heated gases



May 6, 1930. MINOR 1,757,053

METHOD OF AND APPARATUS FOR CURING RUBBER ARTICLES BY THE CIRCULATION OFHEATED GASES Filed Aug. 28, 1926 x M a Ex U fl 331 A aUmo/ e S EPatented May 6, 1930 T D STATE mma? n MIhfOR, on ossmme,rinwlionxjassrenon, BY mnsnn-iissrenmnivrsiro TEE LI ID cannolvic'conronarrolv, A. 'conrona'rron or DELAWARE memos 0am hummus agtimesmmations B THE cIacuLATIon "or nmrnneasns a Application filed august28,1926, Serial No. 132,140.

This invention relates to a method of rap:-

idly curing, molded rubber goods bythe continuous circulation of heatedinert gases, as carbon dioxide; (CO and to apparatus for carrying outsaid method. x

The objectiof my present invention is to accelerate the curing of rubberarticles and in particularly large sized articles such as truck tires orlikeheavy rubber goods where- .in it is found difiicultto effect the"cure throughout the thicknessthereof. At present. it is the practice tocure these articles in watch case heaters. But this operation isunsatisfactory and expensive for various rea-' sons, including the timerequired for the heat to penetrate the rubber sufliciently to cure theinnerplies. a Attempts to accelerate the cure by applying pressure withhot water on the inside have not been satisfactory owing to theformation of air pockets and other attending difiicultiesincludingthecost. and danger of removing thehot water, from the air bags.="

The beneficial effects of carbon dioxide;

(00 when applied to an air bag, for-the curing ofrubbertubes forexample, is known as a result of my prior investigations and discoveries and in my copending application Serial 1% have disclosed andclaim apparatus for and a method of preheating a gas for the purpose ofaccelerating the cure, This discovery I- deem of great importance;Heretofore rec-- ognized beneficial and desirable results obtained bythe use of carbon dioxide in the; curing of rubber goods, as tubesfor'example',

was not deemed possible in the use 'of-the-gas because it was thought tobe impracti'calt'o add suflicient heat units to a gas in'order'to cited;the cure.

I have discovered that not only am I en abled, to elfect a rapid andefficient cure'of' the thinner rubber goods as tubes andthe like, butbymy present improved mode of op.-

eration Iam enabled to rapidly andsuccess fully cure even the heavyarticles such for exeffective.

0. 132,139, filed'August 28,1926, If

of the inflowing and outfiowing heavy truck tires. While I preample asthe fer-carbon dioxide'tClO as the preferred inert 'or'non-oxidiz'inggas for use in carrying out my invention, I do not, of course, therebylimlt'my invention to; the useofthis gas, as nitrogen (N), flue gasesthe like may be used; 'Furthermore,"while this invention is described inits relation to airbags used in whereby the attending named'diificultiesare overcome and I am enabled to convey sufficient heat units by aninert gas, as carbon dioxide, =for' quickly and etl'ectivelyj curingeven the very heavy rubber truck tires. To

more specifically illustrate my invention,

any means whereby the heated'gasis caused to circulate forreh'eating andreturn will be As a "specific instance I have discovered that by placingtwo valves in an air bag, and 'prefer'ably on opposite sides, thatis,one'for the inlet-of the preheated gas and one for 'itsoutlet,thatIlam'able to secure a circulation of the heated gas through thearticle, by reasonof the d-ifi'erence in densities gases. I fur-- therfind'that by bleedmg oil' a circulation is 'much more efiicient onaccount of the resulting'pressure difi'erence. The gas thusremoved isvpreferably returned'to the gasometer for recovery and recirculation.

The main portion of, the gas is however continuously recirculateddirectly through a withdrawn gas it'is necessary to constantly of theheated gas to convey the required thersmall amount. of the gas "from thereturn conduit that the heating-lmechanism. To compensate for the q pmalunits, Iprovide controllable means for curing molded rubberf goods ofvarying mass and the cure is quickly and economically acor heating thegas. The heated I -;passes1by the supply-pipe 24 and its v'alvecomplished with the added beneficial results growing from the use of thegas, as carbon is suited for carrying out my improved method. In saidapparatus I use a source of gas supply 20, prov ded with an expansiontank 21, a pressure heater 22 through which the as is conducted throughthe heating coil 23 gas then 25 into the'air bag-26 of the1watch'caseheater 27. The hot gas supply pipe 24 is provided with an inlet va We 28'for admitting thehea'ted gas into the air bag and preferably on theside opposite I provide the return. pi e or line 30 withan outlet valve3l'f0r esta lishing circulation of. the heatconveying ,inert gasascarbon dioxide. The returnline 30 is also provided with. a branch 32having a valve 33 through which a small amount of the returning gas isbled ofi ordiverted to the gasometer (not shown). Valves 34 and 35(check valves; respectively control the recirculatin 'an inflowinggases. Heat is supplied to the pressure heater 22 by any convenient.means but preferably bya steam'pipe 40 for conducting steam from thevulcan1zing heater directly into the pressure heater but without theheatercoil 23. Condensation products are withdrawn from. the pressureheater by atrap 41. 0 1 a Having now described my nvent on what I claimas new and useful and desire to secure by'Letters Patent is:

1 The method of cu'rin r ubber articles by circulating hot gases whiccomprises heatin the curing gas and then causmg sa1d heate sure underwhich it is supplie circulatin gas to be circulated repeatedly tothearticle to be cured. and then accelerating the circulationof the gaswithout varying the press to cause sa1d gas 'toYtake on additional heatunits for iastening the cure.

2.,The method ofcurin rubber articles by re-heating carbon dioxi e (COthen con-- u'ctin said pre-heated carbon 'dioxide to i I the articletoibecuredto giveup some of its heat units and then accelerating theflowof thecarbon dioxide without var ng the pressure; under which it 'is'supplie ,to cause ad.- 7

, ditiona'l heat units tobe supplied for effectin g a rapid cure.

3. In an apparatus 7 ticles by the circulation of heatedjgas, the

I vide a combination of a source ofgas supplyto proaseous medium,v means.for heating said me ium, means forconveying said heated ,mediumtothe'articles tobe cured and means for "continuously; recirculatingsaid gaseous medium throug the heating means without affecting thepressure of supply from the source.

- 4. In an apparatus for curing rubber articlesby the circulation ofheated gas, the

combination of a source of gas supply to procombinationof a sourceof,gassupply to prov1def a gaseous n edlum, jm'eans for heating sa1dmedlum, means for continuously c1rculating saidheated mediumto. thearticlesand away fromthe articles under oing the cure,

means for bleeding oil aportlon of said gas from the clrculatingsystemand means for constantly replenishing fresh gas from the supply sourceto offset the gas bled ofi.

' 6. The method of. curing'rubber bycirculating hot gases thereto andwhich consists in heatingthe curing gas supplied from a supply sourceunder uniform'pressure, then 1 causing the heated gas tobe recirculatedto the rubberto supply additional heat units thereto, and acceleratingsaid recirculation by causinga pre'ssure diflerence to be set up in thecirculatin system. i

7. The metho of curing rubber articles which consists in continuouslycirculating carbon-dioxlde gas to the articles and ac-' celeratinga thecirculatory flow thereof.

through a preheater by bleeding ofi a'small portion thereof withoutvarying the" pressure under. which it is suppliedyto increase 'thesupply of heat units .to' the material tobe treated, thereby hasteningthe curing action -ofthe as I 8. T e method of-curing rubberwhichconsists in constantly supplymg'under uniform 1 pressure a curingmedium to thearticles to be treated, from a source of'supply through apreheating -device, and tapping oflf'aportion of the circulating mediumfrom thecir- 1 culatory system, to increase the speed: of flow ofsuchniedium in the system.

9.-.The method-of curing rubber articles which. consists inconstantly suplying underuniform ressurje a curing me ium-to the articles toe-treatedfrom 'a source of supply through a preheating device,aandspeeding up thecuring action. of the. medium by settinglup a pressurediflerence in a portion of p v t p the circulating system-withoutvarying the forcuring rubber arpressureunder which the "curing medium issuppliedtothe system. 7

10. The method of curing rubber which consists-in circulating a-curingmedium to the articlesto, be treated under uniform-pressure} cuating-medium cm the circulating supply to increase the speed of flowthereof in the circulating system, and replacing in the circulatingsystem the portion of curm medium tapped ofi therefrom, by supp yingadditional medium from the source to the circulating system.

In testimony whereof I have hereunto set my hand on this 17th day ofAugust A. D.,

HENRY R. MINOR.

